The most common known electronic methods to measure wheel alignment are described below.
All well-known methods and systems for measuring of wheel alignment are based on using electronic and optoelectronic sensors with necessary stability in a given range of measured parameters; and those sensors are mounted directly on the wheel. The methods are based on application of electronic and optoelectronic sensor systems that form measuring units mounted on wheels of the vehicle. Measurement results obtained with measuring unit sensors are processed using a microprocessor system. Data from a preprocessing system is transmitted to a personal or industrial computer for final processing and information display. The measurement process is controlled from a computer or directly from wheel sensors. The methods ensure simultaneous control of all wheel angles. Measuring units contain a set of CCD sensors for measuring angles in horizontal plane (toe-in). Tilt sensors (inclinometers) are used to measure vertical angles in the longitudinal (steering wheel axle caster angle) and transverse (camber angle and steering wheel axle tilt angle) direction. The main disadvantages of the methods are: the complexity of measuring units and, as a consequence, a long time required to mount them on the wheels, high power consumption by wheel measuring unit sensors, low impact resistance of sensors, the requirement to align and center measuring units to the wheels of the vehicle.
Other known methods and systems are based on the use of computer vision. Measurements are performed by processing of measuring data obtained when using flash light emitters on special targets placed on the wheels of the vehicle and recording with video cameras the radiation pulses reflected from the targets. The video cameras and emitters are built using CCD technology. Measurement results obtained with the video cameras are processed using a microprocessor system. Measurement results are processed using a personal or industrial computer that are installed remotely. The main disadvantages of the method are: restrictions on spatial system configuration and sizes of the tested vehicles imposed to ensure target visibility by video cameras.